105 lines
2.4 KiB
C++
105 lines
2.4 KiB
C++
//
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// traits/prefer_member.hpp
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// ~~~~~~~~~~~~~~~~~~~~~~~~
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//
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// Copyright (c) 2003-2024 Christopher M. Kohlhoff (chris at kohlhoff dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#ifndef ASIO_TRAITS_PREFER_MEMBER_HPP
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#define ASIO_TRAITS_PREFER_MEMBER_HPP
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#if defined(_MSC_VER) && (_MSC_VER >= 1200)
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# pragma once
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#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
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#include "asio/detail/config.hpp"
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#include "asio/detail/type_traits.hpp"
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#if defined(ASIO_HAS_WORKING_EXPRESSION_SFINAE)
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# define ASIO_HAS_DEDUCED_PREFER_MEMBER_TRAIT 1
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#endif // defined(ASIO_HAS_WORKING_EXPRESSION_SFINAE)
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#include "asio/detail/push_options.hpp"
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namespace asio {
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namespace traits {
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template <typename T, typename Property, typename = void>
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struct prefer_member_default;
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template <typename T, typename Property, typename = void>
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struct prefer_member;
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} // namespace traits
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namespace detail {
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struct no_prefer_member
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{
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static constexpr bool is_valid = false;
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static constexpr bool is_noexcept = false;
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};
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#if defined(ASIO_HAS_DEDUCED_PREFER_MEMBER_TRAIT)
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template <typename T, typename Property, typename = void>
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struct prefer_member_trait : no_prefer_member
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{
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};
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template <typename T, typename Property>
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struct prefer_member_trait<T, Property,
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void_t<
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decltype(declval<T>().prefer(declval<Property>()))
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>>
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{
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static constexpr bool is_valid = true;
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using result_type = decltype(
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declval<T>().prefer(declval<Property>()));
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static constexpr bool is_noexcept =
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noexcept(declval<T>().prefer(declval<Property>()));
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};
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#else // defined(ASIO_HAS_DEDUCED_PREFER_MEMBER_TRAIT)
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template <typename T, typename Property, typename = void>
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struct prefer_member_trait :
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conditional_t<
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is_same<T, decay_t<T>>::value
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&& is_same<Property, decay_t<Property>>::value,
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no_prefer_member,
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traits::prefer_member<
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decay_t<T>,
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decay_t<Property>>
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>
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{
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};
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#endif // defined(ASIO_HAS_DEDUCED_PREFER_MEMBER_TRAIT)
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} // namespace detail
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namespace traits {
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template <typename T, typename Property, typename>
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struct prefer_member_default :
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detail::prefer_member_trait<T, Property>
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{
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};
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template <typename T, typename Property, typename>
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struct prefer_member :
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prefer_member_default<T, Property>
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{
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};
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} // namespace traits
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} // namespace asio
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#include "asio/detail/pop_options.hpp"
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#endif // ASIO_TRAITS_PREFER_MEMBER_HPP
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